1. Field of the Invention
Embodiments of the invention generally relate to methods of making a magnetoresistive reader structure for sensing data stored on magnetic media.
2. Description of the Related Art
In an electronic data storage and retrieval system, a magnetic head typically includes a reader portion having a magnetoresistive (MR) sensor for retrieving magnetically encoded information stored on a magnetic recording medium or disk. The MR sensor includes multiple layers and operates based on a change of resistance of the MR sensor in the presence of a magnetic field. During a read operation, a bias current is passed through the MR sensor. Magnetic flux emanating from a surface of the recording medium causes rotation of a magnetization vector of a sensing or free layer of the MR sensor, which in turn causes the change in resistance of the MR sensor. The change in resistance of the read element is detected by passing a sense current through the read element, and then measuring the change in bias voltage across the read element to generate a read signal. This signal can then be converted and manipulated by an external circuitry as necessary. A hard magnetic bias structure can be used to stabilize the magnetic movement of the free layer to provide a noise-free response from the MR sensor. In construction of the MR sensor, depositing hard bias layers on both sides of the MR sensor accomplishes this stabilization.
As storage density on the recording medium increases, a track width of the MR sensor must be made narrower to enable accurate read sensitivity. Signal resolution depends on the track width of the MR sensor being narrower than track spacing on the recording medium. Several prior approaches for defining the track width of the MR sensor exist but have disadvantages. For example, material deposited to form the hard magnetic bias structure may remain above the MR sensor without any ability to be lifted off due to a photoresist lacking sufficient thickness as a result of its poor mill resistance at small track width. Further, attempts to remove unwanted portions of the hard magnetic bias structure tend to create unevenness or thinning of the hard magnetic bias structure and thereby prevent proper stabilization during use.
Therefore, there exists a need for processes of fabricating narrow magnetoresistive sensors to improve properties of the sensors.